Re: [codec] I-D Action: draft-ietf-codec-oggopus-03.txt

Calvin Walton <> Fri, 28 February 2014 14:48 UTC

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From: Calvin Walton <>
To: Ralph Giles <>
Date: Fri, 28 Feb 2014 09:48:22 -0500
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Subject: Re: [codec] I-D Action: draft-ietf-codec-oggopus-03.txt
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On Fri, 2014-02-07 at 16:21 -0800, Ralph Giles wrote:
> On 2014-02-07 3:57 PM, wrote:
> >       Title           : Ogg Encapsulation for the Opus Audio Codec
> > 	Filename        : draft-ietf-codec-oggopus-03.txt
> I've posted a new version of the Ogg Encapsulation draft for Opus.

> (2) We haven't addressed Calvin Walton's questions about the various
> gain headers.

I just want to try to restate and clarify my opinion on this a bit:

The ReplayGain tags are application-specific metadata tags defined by a
specification that is managed externally to the IETF[1].

As such, I don't think it's appropriate for the Ogg Opus specification
to state whether or not the REPLAYGAIN tags should be present in the
file, or their specific semantics. Any required changes for handling
ReplayGain in Ogg Opus should probably be done in the ReplayGain specs


One question I'm not sure about. Is the proposed R128_TRACK_GAIN field
supposed to be a generic vorbis comment standard that can be used in
multiple formats? (e.g. Ogg Vorbis, Flac), or is it intended only for
use in Opus?

If the former, it should probably be proposed in a more general way.
Inasmuch as there is no real standardization organization for
multi-format vorbis comment fields, a discussion on the HydrogenAudio
forums may be a good place to see if there is any interest in adopting
the comment format.

Having a uniform set of tag names for vorbis comments is advantageous to
people building music players and decoding libraries, since it means
that vorbis comment parsing code can be shared between multiple formats.

1) It's currently published on the HydrogenAudio wiki.
Current standard (David Robinson's original calculation algorithm)
Proposed revision (updated algorithm based on EBU-R128 with gain offset)

Calvin Walton <>